Method of precasting concrete stair structures



F. KOGL 2,289,439

METHOD OF PRECASTING CONCRETE STAIR STRUCTURES July 14, 1942.

4 Sheets-Sheet 1 Filed June 12, 1939 .eAMe 1 061.

' Jqly14,1942. F, KO L 2,289,439

METHOD OF PRECASTING CONCRETE STAIR STRUCTURES Filed June 12, 1959 4Sheets-Sheet 2 July 14, 1942.- F. KOGL 2,289,439

METHOD OF PRECASTING CONCRETE STAIR STRUCTURES Filed June 12, 1939 4Sheets-Sheet 3 Fen IVK Aom.

F. KOGL 2,289,439

METHOD OF PRECASTING CONCRETE STAIR STRUCTURES July 14, 1942.

Filed June 12, 1939 4 Sheets-Sheet 4 S a a 7 n/ W 2 3 m 11%.?

a a M Patented July 14, 1942 METHOD OF PRECASTING CONCRETE STAIRSTRUCTURES Frank Kogl, St. Paul, Minn., assignor of two and one-half percent to Walter H. Carlson, two and one-half per cent to Ora E. Carlson,four per cent to Minnie C. Schneider, four per cent to Genevieve Clarkand ten per cent to Ruby S.

McBride, all of St. Paul, Minn.

Application June 12, 1939, Serial No. 278,711

Claims.

My invention relates to an apparatus and method for precasting concretestair structures.

The primary object of my invention is to provide an improved mold formfor the monolithic casting of concrete stairs or stoopsparticularlysuitable for use at the outer doors of a residence or at lawn terraces,and to provide a mold of such nature that it maybe adjusted to cast anyof several numbers of steps and to provide a surmounting platform of aselected length or area, thus suiting the stairs to each particularinstallation. Another object is to provide a mold form of this kindwhich may be set up and dismantled in progressive and retrogressiveorder to permit it to be properly filled with the cementitious mixtureand then 'to permit the cast structure to be exposed for inspection andremoval without difiiculty or damage. A further object is to provide amold form which may be arranged to cast a nosing or marginal projectionon each step tread and a lower marginal base ledge or shoulder aroundthe structure to form abase for brick vencering or buttresses on thefinished steps.

Still another and important object of my invention is to provide animproved method for the monolithic precasting of stair structures inwhich the cementitious mixture is poured into an inverted molddownwardly toward what are finally the finished surfaces of the stepsand with vent means provided for the escape and exudation of excess airand water to insure the proper settling and setting of the material. .Itis thus possible to provide a finished product having tread and risersurfaces .of any desired texture or surface configuration without the.necessity of additional or supplementary finishing operations of anykind.

These and other more detailed and specific objects will be disclosed inthe course of the following specification, reference being had toi theaccompanying drawings, in Which Fig. 1 is a side-elevation of the moldor apparatus setup for casting a series of four steps, a platform andsurrounding base for 'buttressing.

Fig. 2 is an enlarged fragmentary section along the line 2-2 in Fig. 1.

Fig. 3' is .an enlarged sectional detail view of a connecting means formounting and connecting the outer riser and tread forms.

Fig. 4 is a plan View of the mold shown in Fig. 1, sections being brokenaway to better disclose interior construction.

Fig. -5 is a longitudinal vertical sectional View through the mold.showing the same inverted on a supporting standand partially filled withthe cementitious mixture.

Fig. 6 is an enlarged vertical cross section along the line 6-6 in Fig.1.

Fig. 7 is a perspective View, on a reduced scale, showing the steps castby the form and with a portion broken away and in section to show theconstruction thereof.

Fig. 8 is a fragmentary side elevation, also on a reduced scale, showingthe form assembled for casting only two steps and a narrowplatform.

Referring now with more particularity and by reference characters to thedrawings, the mold or apparatus constituting my invention isindicatedgenerally at A and is seen to comprise as its basic elements anouterform B' and inner form C. These forms are assembled, in the set upcondition of the mold shown in Figs. 1, 4, and 5., to provideintervening cavities and recesses which when filled with, thecementitious mixture will ."form and cast a step structure of the typeshown Fig. 7.. This structure comprises a series of four steps eachhaving a tread T, and a riser R, a surmounting Iflat platform P, thepanelled sides or side walls S and the surrounding lower marginal ledgeor base L, all of monolithic construction, as shown. The wall thicknessat all points may be of any desired dimension but it is of courseunderstood that the entire underside of the structure is hollow in orderto reduce weight and quantity of material required. A nosing N surroundsthe ends and outer exposed edge of each tread Tas clearly shown.

Turning now to the construction of the mold itself, the outer form .3thereof comprises a plurality of .side sections or side plates which, intheir assembled relation, are set and joined on edge vertically anddefine the :outer surfaces of the stair sides S. Each side section is ofa width (vertically) corresponding to the height of the risers R and.the sections accordingly are in number equal, at each side .ofv theform, to the number of steps to :be cast. In the mold shown a maximum offour steps may be cast and the side sections are accordingly representedby the reference numerals l0, [1,, I2, and I3 in progressive order, itbeing understood, however, that the mold may be constructed to have amaximum step capacity either more or less than that here shown.

These side sections l-ll through I3 are formed of fiat metal sheets orplates of rectangular shape and grow progressively shorter eachsuccessive step upward, to thereby terminate at a common vertical planeat their rear ends l4. The

margins are braced by angle irons designated generally at l5, spotwelded or otherwise secured in place, and which also form means forattaching the sections to each other and to other component parts of themold. To this end, and as a representative fastening means, I providethe angle irons with registering apertures IS in their outwardly turnedwebs and through which are placed diametrically slotted pins H for thereception of wedges or keys [8 which, when driven tight, hold the partsrigidly together. This type of fastener meets the requirement of a rigidand quickly manipulated means for assembling the sections, but I may ofcourse employ bolts, spring latches, or other suitable means as may bedesired.

In the mold assembly, therefore, four of the side sections are set up onedge and secured together at each side of the mold, and present a planeinner surface well adapted to form and define the outer sides of thesteps. Runners or strips I9 of rounded cross section may be secured, inaligned parts or sections, to the inner surfaces of the side sectionsIl3 as shown in order to form depressed grooves G in the stair sides Sand give a panelled effect thereto. Other suitable ornamentation mayalso be provided as desired, and particularly is this true since theside sections are progressively removable from the cast structure aswill hereinafter appear,

The forwardly projecting forward ends and upper edges of the sidesections I0 through [3 form supports for the four riser and treadforming members or outer riser and tread forms 20, 2|, 22, and 23 whichare removably secured transversely across these edges of the assembledmold sides. Each of these forms 20 through 23 is substantially identicalin shape and size and comprises a vertical riser plate 24 and horizontaltread plate 25 forming a right angled structure as shown. The ends ofthe forms are provided with notches 26 in both their vertical andhorizontal portions for the reception of clamp bolts 2! which arepivoted at their ends 21?. to each side section II] to l3 in position toswing at their free ends into said notches. The vertical plates 24 arethen drawn tight against the forward angle irons l by wing nuts 28screwed on the forwardly directed bolts 21 and the horizontal plates 25,which are braced by the end angle irons 29, are similarly drawn tight bythe wing nuts 3|] screwed upon the upwardly directed draw bolts asclearly shown in Fig. 1.

It will be noted that the forwardly projecting upper edges of each sidesection In through I3 are provided with outwardly bulged and roundedportions 3| and the connecting frontal edge portions of the plates 24and 25 of each outer tread and riser form 20 through 23 are similarlyformed as designated at 32, the said portions 3| being coped at 33 intothe portions 32 to fit nicely thereinto. As a result the ends andforward edges of the treads T of the finished stair structure will beprovided with the desired nosing N I through 23 are turned smoothlyforward a short 45 which surrounds the forward and lateral edges of themold and is secured at the sides thereto by pins I! and wedges I8 asshown. The interconnection between the forms 20 through 23 providesrigid fastening means at their edges but permits the forms to be swungclear in progressive order as shown in Fig. 1, and as will hereinafterappear. The meeting edges of the forms abut in a common plane to providea smooth surface for the treads T and if so desired I may employ in lieuof the brackets 35 and tongues 36, the clips 4| and similarly formedtongues or hooks 36 as detailed in Fig, 3.

The inner form C is somewhat similarly constructed and comprises, in theembodiment shown, four inner side sections 42, 43, 44, and 45 at eachside and which are formed of sheet material with marginal angle irons 46secured to their inner faces. These inner side sections are set up onedge within the mold and are secured together by pins 41 and wedges 48which pass through registering aperture 49 in the inwardly turned websof the horizontal angle irons 4'6. The necessary forms for defining theinner surfaces of the stair sides 5 are thus assemble-d and of coursethese inner sides are spaced from the outer sides of the mold to providea suitable wall thickness. For this purpose the lower inner sidesections 42 are made sufficiently wide (vertically) to fall flush withthe lower edges of the trough form 40, and a cross frame 50 of angleiron is secured at its ends to both these side sections and the troughform by means of pins 5| and wedges 52 which lock the frame to the lowerangle iron 46 and to marginal angle irons 53 secured to said troughform. The frame 50 thus serves to properly space the assembled innermold sides in the mold and to support the inner and outer forms as willbe apparent.

The inner surfaces of the risers R and treads T are defined by innerriser and tread forms which in this case take the form of separatevertically disposed and transversely extended inner riser plates 54 andsimilarly extended but horizontally laid inner tread plates 55. Theforward ends and upper forward margins of the inner side sections 42through 45 are arranged to fall short of the respective outer riser andtread forming portions 24 and 25 of the outer form and the inner riserplates 54 are therefore secured flush with said forward ends by means ofpins 56 which are inserted through apertured, interdigitating lugs 51and 58 secured, as by welding, to adjacent ends of the inner sidesections and said inner riser plates. Upper and lower transverse marginsof these inner riser plates are turned, in nicely rounded shape,respectively rearwardly and forwardly, as indicated at 59, to form seatsor footings upon which the inner tread plates 55 may be rested at theirmargins. The said margins 59 are provided with aligned forks or brackets60 in which may then be placed the removable retaining bolts 6| whichtraverse the inner tread plates 55 and have their headed ends 62 hookedin the forward forks. Wing nuts means 63 are turned up on the rear endsof the bolts to rigidly retain said inner tread plates in place asclearly-shown in Fig. 5. The foregoing assembly spaces the innerriserand tread plates inwardly to provide suitable wall thickness for therisers and treads as will be evident.

The uppermost inner tread plate 55 may well be formed as anintegral-continuation of the adjacent inner'riser pl'ate5'4 as it ishere shown.

The uppermost treadT defined by the tread forming portions 25 and 55 fthe mold may be integrally extended in the form of the platform P, thisbeing accomplished by the provision of outer extension sections 64 andinner extension sections 65 which are identical in number, width, andconstruction to their complementary side section's I0 through I 3 and 42through 45. These extensions '64 and 65 are of equal length, however,and areprovided with marginal angle irons 6'6 and 61 on theirouter andinner faces respectively. Pins 68 and wedges '69 thus may be employedtofasten the'individua'l sections together edgew'ise and also to securethe assembled inner and outer extension mold sides thus formed to therear ends of the inner and outer mold forms as clearly shown. The troughform 48 is of sufficient length to fit along lower edges of theseextension sides and the'inner and outer platform plates 10 and Hcomplete the extension of the mold. These plates 10 and H are of coursesecured marginally to the uppermost tread formtransverse angleirons 12are secured to the abutting edges for thereception of the pins 13, andwedges 14 are inserted through the pins to draw the parts tightlytogether. Clamp bolts 82 and wing nuts 83 are also provided for lockingthe plate ll in a manner similar to the outer tread plates 25.

The rear end of the mold is closed by an adjustable, substantiallyU-shaped yoke or end member 15 which is of such width that it may slipnicely within the opening between the outer and inner'forms B and C. Forsupporting the member 15 in position I provide cross bars 16 which maybe secured to the rear angle irons on the inner and outer forms by pins11 and Wedges 18 or othersuitable means, and which are aper: turedtos'li'dably pass rods 19 secured at their inner ends at 80 to said endmember. Collars 8| are placed on therods at'each side of the cross bars16 and 'it will be apparent that the end member 15 may be secured at anyadjusted position within the form to thus determine the length for-Wardly and rearwardly of the completed structure. This end assembly mayfurthermore be assembled either within the rearward extension of themold or within the main portion thereof togive a further variation insize.

In the actual operation of the mold and its use for-casting the stairstructure described, the outer'form B is first completely assembled andis supported in an inverted position upon a work table or other'suitablesupport with a frame 85 having uprights 86 of graduatel length forholding the form level. The inner form C is also completely assembled,except for the inner tread plates '55, and is then supported inside theouter form in the manner described by the frame 50, and the pouring maybe started. The extension members 64, 65, I0, and H are of course alsoassembled if the type and length of platform desired requires their use.

The cementitious mixture is then poured in the open sides of the moldand through the openings provided by the detached plates 55, and

' mg members 55 and 25, and for this purpose asffast as'the treadportionsfill these plates are put in -place. The operation continuesrapidly and without interruption until all parts of themolda're-complet'ely filled, after which the mold is allowed to setuntil the mixture hardens. Uhder some circumstances, and where themixture is of proper consistency, the-pouring may be done into the moldsidesonly, leaving the plates 55 in pl ce and thl ls saving the timerequired T01 their replacement, when the mold is made ready for useagain. V

The trough-form 40 maybe filled, or not, accordingly ass, baseledge Lmay or may not .be desired, and it is of course readily possible to fillonly to the line 81 shown in Fig. 5,where the ledge is not required. Tofacilitate the assembly of the various mold forms, dowelpins 88a areprovided at appropriate locations on the meeting surfaces of the parts.

When the mixture has hardened sufficiently the plates 55 are removed andby prying upwardly the entire inner form C is pulled free. Cross bars orsome similar members (not shown) replace the frame'56 to temporarilyhold the molded structure in the outer form, and the form is nowreverted by means of a bail 88 whichisconnected to a crane orotherlifting means (not shown). The lower ends of the bail are pivoted uponshouldered clamp nuts 89 which screw upon the studs 90 of slide blocks9! sli'dably mountedin channels 92 secured to the sides of the mold, andthese channels are formed in angu-larly extended sectionsso thatadjustments may 'be made to properly balance the mold in the bail foreasy turning or inverting and reverting movements therein.

With the mold in this reverted position the outer tread and riserplates28 through'23 are removed in progressive order, thus freeing the sidesof the molds which are then pulled clear, leaving the cast structurefreeof the mold for further curingbefo're installation. The mold is thenready for further use-and it will be evident that since the sides arenot taken apart, the operation of assembling and disassembling the moldmay be carried out rapidly and easily.

It will be noted that in this operation the mold parts all-are swung orpulled away from the finished surfaces of the casting and the removal ofparts is thus greatly facilitated. This operation further makes itpossible to impress any desired ornamentation on the finished-surfacesof the casting in either intaglio -or relief, and {the treads T may ifdesired be provided with nonskid bosses or beads 95 by forming complementary impressions 96 in the outer tread forming plates 25, as shown onlyin Fig. 6.

An important feature of my invention resides in the adjustability of theform and the ease with which the size of the completed structure may bevaried. Thus the length, and the platform area, may be readily adjustedas desired by the use, or the elimination of, the mold extension members64,65, 10, and "H and adjustment of the end member 95. Also any'numberof steps, from one to four in the specific embodiment shown, by usingthe desired number of inner and outer side sections and theircorresponding riser and tread forming cross member. The mold is shown inFig. 8 as set up for casting only two steps, and it is thought that themanner of making these adjustments will be evident without furtherdescription. To facilitate these adjustments, however, the holes for thefastening pins l1 and 41 are arranged so that the base sections I8 and42 may be readily aligned with and connected to any of the other uppersections. The Width of the steps may of course be varied by theprovision of riser and tread forming members of any desired length.

In the practice of molding the stair structure by my improved mold asdescribed, there is embodied and carried out also an improved method ofdoing such work. This resides in the provision of a mold in which themembers 24 and 25 which define and mold the finished tread and risersurfaces are downwardly disposed with reference to the point at whichthe cementitious mixture is poured into the mold. Accordingly thepouring is toward said finish surfaces and the normal tendency of themixture to settle causes it to assume a perfectly smooth texture onthese surfaces. Such obviously would not be the case were the finishedsurface uppermost as has hitherto been the practice. Furthermore, thematerial as it is poured down into the tread forming portions of themold, where greatest exterior smoothness or nicety of finish is desired,is compressed by weight of the material within contiguous riser and sideforming portions of the mold. The upper members 55 confining the mixturein these tread forming recesses of the mold are provided with spacedvent openings 93 so that excess water and air bubbles may exudetherethrough, and further insure the proper density in the treads. As afurther aid in settling the material vibratory effects may be used,either by bodily shaking the mold or by the application of an air hammeror similar tool locally to various parts of the mold.

The inner mold form C may also be conceivably of one piece construction,particularly where the trough form 40 is not used and such variationfrom the disclosed construction is held to be within the scope of myinvention.

The type of mixture employed may be any of those known to personsskilled in the art, and an advantageous result of using the lighterforms of aggregate now on the market will result in the ease with whichthe cast structure may be handled and installed. Reinforcing rods orsimilar material, designated at 94 in Fig. 6, may of course be installedas the casting operation proceeds to further aid in the provision of alight but strong structure.

The use of metal for all parts of the form prevents checking due to theshrinkage and moisture absorption of the more usual wood form, and aidsin the provision of a practical and long lasting structure. Propersetting of the mixture is also increased since the entire operation maybe carried out indoors under controlled temperature and is not thereforesubject to the vagaries of outdoor weather conditions.

It is understood that suitable modifications may be made in thestructure as disclosed, provided such modifications come within thespirit and scope of the appended claims. Having now therefore fullyillustrated and described my invention, what I claim to be new anddesire to protect by Letters Patent is:

1. The method of precasting a concrete stair structure having a seriesof integrally formed steps and sides in a mold having members forforming the treads and risers of the steps and the said sides, whichcomprises positioning the mold with the tread forming members invertedwith respect to the normal position of the steps and so that said treadforming members are substantially level and constitute the bottom of themold, pouring a wet cementitious material downwardly into the sides ofthe mold to fill the spaces between the tread, riser and side formingmembers, and finally removing the mold when the structure has hardened.

2. The method of casting a monolithic stair structure having a pluralityof steps in a mold having inner and outer spaced forms shaped to definethe corresponding surfaces of the component treads and risers, whichincludes positioning the mold so that the cast structure will initiallybe in upside-down position, pouring a wet cementitious material betweenthe forms to fill the spaces forming the then lowermost step and thenthe remaining steps in succession, removing the inner form when thematerial has hardened, reverting the outer form to dispose the structurein normal position, and then removing the said outer form.

3. The method of casting a monolithic stair structure having a pluralityof steps in a mold having inner and outer spaced forms shaped to definethe corresponding surfaces of the steps and with pouring openings in theinner form adjacent the position of each step, which includes invertingthe mold to dispose the steps initially in an upside down position,pouring a wet cementitious mixture through first the lowermost openingin the inner form to fill the lower space between the forms, closingsaid opening when the pouring thereat is completed, repeating thepouring and closing operations at each step in upward succession,removing the inner form when the material has hardened, reverting themold, and removing the outer form.

4. The method of casting a monolithic stair structure having a pluralityof steps in a mold having inner and outer spaced forms shaped to definethe corresponding surfaces of the component treads and risers, whichincludes positioning the mold so that the cast structure will initiallybe in upside-down position, pouring a wet cementitious material betweenthe forms to fill the spaces forming the then lowermost step and thenthe remaining steps in succession, and separately removing the inner andouter forms when the material has hardened.

5. The method of casting a monolithic stair structure having a pluralityof steps in a mold having inner and outer spaced forms shaped to definethe corresponding surfaces of the component treads and risers, whichincludes positioning the mold so that the cast structure will initiallybe in upside-down position, pouring a wet cementitious material betweenthe forms to fill the spaces forming the then lowermost step and thenthe remaining steps in succession, reverting the mold when the materialhas hardened, and removing the inner and outer forms.

FRANK KOGL.

